1)
- Top picture = Beryllium-7
- Bottom picture = Beryllium-8
Note: Both are Beryllium, but are isotopes.
General steps ( can be used on similar questions):
I. Count the # of protons in the atom.
II. Go to the periodic table and look for atomic #, which is equal to # of protons in an atom.
III. Count the # of neutrons.
IV. # of neutrons + # of protons = mass number. (the number after the hyphen)
2)
Top picture:
- Atomic # = 4
- p = 4
- e = 4
- n = 3
- mass = 1.17*10^-23 g
Bottom picture:
- Atomic # = 4
- p = 4
- e = 4
- n = 4
- mass = 1.33*10^-23g
General steps to find atomic #, p, n, and e:
I. Count the # of protons in the atom to get p.
II. Go to the periodic table and look for atomic #, which is equal to # of protons in an atom.
III. Count the # of electrons to get e.
IV. Count the # of neutrons to get n.
General steps to calculate mass:
I. Find the molar mass of the element on the periodic table. Or, do a web search.
II. Multiply molar mass with 6.02*10^23 (Avogadro’s Number)
III. Cancel out any units and solve.
In the pictures are the steps I used to calculate the mass for your particular problem.